I have been working in an IT environment since high school and so I have learned a few tricks. Below are steps that if you follow and maintain them your PC is guaranteed to stay at tip top shape and will never slow down.
Keep your PC Running Fast
I never leave the house without the following small applications on my flash drive. All of the applications below work on all OS versions including Windows 8 x64.
Download CCleaner. This small (2.51MB) freeware application works wonders. It is made my a company called Piriform. I run it multiple times per day, but that is just because I am obsessive. If ran once a week, you would be fine. After downloading and installing there are two things you will want to do. First, run the cleaner and second, scan for issues in the registry. Depending on how old your computer is and the amount of time since you have cleaned it up, CCleaner might take up to 20 minutes to finish. Normal scan and clean is around 30 seconds if preformed regularly. I have seen this little application remove up to 20GB, yes 20GB!!, which is just absolutely amazing.
Second, download Malwarebytes Anti-Malware. If you have any malware this will catch it. I also recommend Microsoft Security Essentials for 24/7 free anti-virus. If you are running Windows 8 you can skip Microsoft Security Essentials as Windows Defender is already built in.
A classic and yet still useful tool. Go to your start menu, applications, system tools, and run the disk defragmenter. Or you can download Defraggler from the same company that makes CCleaner.
Right click on “My Computer” icon and click the advanced tab. Go to the performance options “settings” tab and unselect every option except for the last two. These last two are the only two that you will notice and so you will want to leave them on.
If you run through these 4 steps, and keep repeating steps #1-3 at least once a week, your PC will keep running at its finest, I promise you.